The present invention relates to hubs, particularly though not exclusively hubs for or incorporated in vehicle wheels, particularly bicycle wheels or motorcycle wheels but also wheels for vehicles with three or more wheels, and is concerned with that type of hub which incorporates a variable ratio transmission system.
Bicycle wheels are known with a hub which incorporates a variable ratio transmission system but this transmission system can only provide a relatively small number of discrete gear ratios. It would be desirable to provide a bicycle wheel with a hub incorporating a transmission system of continuously variable ratio.
There is an ever increasing social and legislative pressure on the manufacturers of motor vehicles to provide engines with a reduced fuel consumption and thus reduced emission of pollutants. One way of achieving these aims is to ensure that the transmission system of the vehicle always uses the optimum gear ratio and this can only be achieved by providing that the transmission system is of continuously or steplessly variable type and thus has an infinite number of gear ratios. One of the results of the pressure referred to above to reduce the fuel consumption and thus the emission of pollutants from engines is that vehicles of so called hybrid type are rapidly increasing in popularity. There is therefore also a need for a transmission system which can simply combine both a mechanical power input and an electrical power input into a single mechanical power output.
It is the object of the present invention to provide a hub incorporating a variable ratio transmission system which fulfils all of the above requirements.